I think I'd have to go with giannini
At least in the anime his voice is SO annoying. Plus at least that I've seen so far his usefulness is less than stellar.
He's a mechanic character but he's also there for the gags and I just wish they'd permanently replace him with

I kind of agree. I didn't want to watch this show but my little brothers did so I got hooked but the 1st few episodes had Reborn making a hell out of Tsuna's life and I got annoyed. I didn't like him before and I don't think I will like him as much since he's still annoying.

Also, 5-year old Lambo... he's annoying. And Haru cause she's too possessive of Tsuna and that attitude goes from just possessive to just annoying.

I hated the Tsuna at the 1st few episodes cause unlike other anime main characters, he needed a bullet to make him courageous and stronger but I liked him after a while when he doesn't act to wimpy anymore.